1. Field of the Invention
The present invention relates to a transmission processing apparatus, a television conference system, a transmission processing method and a memory medium for video/audio signals from plural video/audio sources selectively to a network, and more particularly to a transmission processing apparatus, a television conference system, a transmission processing method and a memory medium capable of adapting to a computer network.
2. Related Background Art
There is already known a configuration of the communication terminal apparatus, capable of transmitting and receiving image and voice by connecting video/audio input/output devices, such as a camera, a video monitor, a microphone, a speaker etc. to a computer (personal computer or work station), and such communication terminal apparatus is already used commonly as the terminal for television or video conference.
A video signal entered from the camera and an audio signal entered from the microphone are respectively digitized, then encoded by a predetermined method and released to a network such as a local area network or a wide area network. The encoded video and audio signals from the network are decoded, and are respectively released from the video monitor and the speaker. The microphone and the speaker are combined with an echo canceller for avoiding echo resulting from voice circulation. The microphone and the speaker may also be constructed as a speaker-phone.
Such television conference system has conventionally been constructed with communication terminals exclusively designed for this purpose, but the recent improvement in the processing ability of the computers has enabled to hold such television or video conference utilizing the ordinary desk-top computers in the office.
In the application of transmitting the video/audio signals to a distant location, there is also known a tele-monitoring system for observing various distant sites.
In image transmission, there is required a high cost in the video capturing device for fetching the output image signal of the camera with digitization and a video compression device for effecting compression encoding. If such devices are provided in the computer of each participant, they are not cost-effective in consideration of the work rate of such devices.
Also in certain applications such as the tele-monitoring system, the image of a site need not necessarily be renewed with a high frame rate but can be transmitted for example with a rate of a frame per second. For such applications, the video compression device with a capacity of 30 frames per second becomes superfluous.